In a fuel tank installed in a motor vehicle, a part of fuel evaporates and generates evaporative emissions. In recent years, such evaporative emissions are drawn as purge air into an intake system of the engine where it is effectively used as fuel, without escaping into the atmosphere. This is intended to prevent pollution and improve efficiency in the use of fuel. While the engine is stopped, such as when the fuel is being supplied to the fuel tank, however, the evaporative emissions are not immediately burnt in the engine. To temporarily store the evaporative emissions in such cases, a canister containing an adsorbent material capable of adsorbing and storing fuel components (such as hydrocarbon) is provided between the fuel tank and the intake system of the engine.
This canister, which is a component of a fuel system, is located outside the cabin or vehicle compartment, and is generally mounted in the engine room, taking account of mounting space and maintainability.
Recently, however, large-sized canisters capable of adsorbing a large amount of fuel components have been prevailing because of an increased size of the fuel tank and more stringent pollution prevention laws. With the canister thus increased in size, the engine room may not be able to provide a space large enough to accommodate the canister. Where the engine room accommodates an engine having a large displacement and equipped with many devices such as a turbocharger, in particular, the canister cannot be suitably mounted in the engine room due to considerable reduction in redundant space available for the canister.
Therefore, mounting the canister in a fuel tank where there is no constraint or limit in terms of space is considered. The fuel tank, however, has components such as a fuel filler tube and a unit gauge for measuring fuel amount attached thereto, and these components incorporated in the fuel tank restrict the mounting position of the canister. Further, the mounting position of the canister must be carefully considered in view of an actual design or layout of the fuel tank itself, rigidity and material of the fuel tank, environmental characteristics of the canister, increased size of the canister and so on.